AT command for hang up call automatically at hardware level

I'm using sim900b to control home appliances via sms . But sometime incoming call interrupts the communication , I used "ATH" command each time I'm getting a new incoming call . When sim900b gets a incoming call , it sends incoming call status to arduino , and checking this arduino sends "ATH \n\r" to sim900b and then it disconnects the call .

I want to is there any alternative way available so that sim900b will automatically disconnect the call by itself , so that I wont need to send any command from arduino to disconnect the call ?